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Govoni S, Loddo P, Spano PF, Trabucchi M. 
“Dopamine receptor sensitivity in brain and retina of rats during aging”. 
Brain Research. 1977;138:565-570.
Age-related changes of neurohormonal, endocrine and autonomic functions have been documented which may be the basis of diverse modes of cell functioning. The unique role of the brain in adaption to environment through its integrations with the entire body makes fascinating the hypothesis that the CNS may play a key role as a pacemaker in the rate of aging. There is much experimental evidence indicating that different neurochemical systems in the brain are modified during aging. Striatal dopamine metabolism is affectedly, the catabolism of norepinephrine in hypothalamus is slowed; dopamine uptake by hypothalamic and striatal synaptosomes appears to be reduced; the sensititivty of adenylate cyclase to catecholamine in cerebellum, cortex, hippocampus and caudate is reduced. All these data confirm the hypothesis of a general decrease in the function of the central nervous system. In this line we have studied the relationships among aging and the dopaminergic system at the level-of dopaminergic receptors. Therefore, in view of recent studies demonstrating in several dopaminergic areas of the CNS a dopamine-stimulated adenylate cyclase which displays many characteristics of a dopamine receptor, we have investigated the activity of dopaminestimulated adenylate cyclase in homogenates of striatum, nucleus accumbens, tuberculum olfactorium, substantia nigra and retina of mature and senescent rats. Mature (2-3-month) or senescent (20-24-month) male Sprague-Dawley rats (Charles River, Calco, Italy) were used in our experiments. Senescent animals with pathological affections (tumors, respiratory infections eĀc.) were excluded from the study. Mature or senescent rats were randomly caged on the same shelves to avoid environmental differences. Rats were housed at constant temperature and humidity and exposed to a light cycle of 12 h a day. Animals had free access to food and water. The different brain areas have been dissected following the method indicated by Horn et al. for nucleus accumbens and tuberculum olfactorium, and by Koslow et al. for substantia nigra. Adenylate cyclase activity was measured following the method of Kebabian et al. with minor modifications. After 3 min of incubation the reaction was stopped by boiling the samples for 3 min. Cyclic AMP was purified and assayed using the method
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